The hydrologic cycle, also known as the water cycle, describes the constant movement of water in various forms, such as liquid, vapor, and ice, on and above the Earth’s surface. The cycle is powered by the sun’s energy, which causes water in the oceans to evaporate and rise into the atmosphere as water vapor. As the vapor cools, it forms clouds and falls back to the surface as precipitation. Some of this precipitation returns to the oceans, while the rest falls on land and either seeps into the soil or flows into rivers and streams. This water eventually makes its way back to the oceans, completing the cycle.